As ICOS and PD1 binding mediate activating, respectively, inhibitory signals, these results might suggest that, irrespectively of B7 expression on AML blasts, CD8+ T cells are more prone to PD-1-mediated apoptosis, while their CD4+ counterparts are more susceptible to activation, but also to activation-induced cell death. The gene discussed is ICOS; the disease is acute myeloid leukemia.